1. Field of the Invention
The present invention relates to a pointing device used as an input device of a personal computer or mobile phone, and more particularly to a magnetic detecting type pointing device for inputting coordinate detection information or vector information by detecting ambient magnetic field changes caused by in the movement of a magnet. In addition, it relates to a magnetic sensor array suitable for these pointing devices, and to a pointing device manipulation adapter.
2. Description of the Related Art
FIG. 4 is a block diagram showing a magnetic detecting circuit of a conventional magnetic detecting type pointing device. In FIG. 4, a detecting section 1 includes four magnetic sensors (such as Hall effect devices, semiconductor magnetoresistive elements, ferro-magnetic magnetoresistive elements, GMR devices) 11. The four Hall effect devices 11 are placed symmetrically two by two along the X and Y axes. A magnet is disposed close to the center of the four Hall effect devices symmetrically placed on the X and Y axes. The output voltages of the Hall effect devices 11 vary in response to the changes in the magnetic field caused by a movement of the magnet. Differential amplifiers 2 differentially amplify the outputs of the Hall effect devices 11 on the X axis and Y axis, respectively. They are preset such that their outputs become zero when the magnetic field in the Z axis direction is symmetric with respect to the origin O, that is, when the magnetization direction of the magnet is in the vertical direction. The system is configured such that the differential amplifiers 2 generate outputs in response to the movement of the magnet, and that a detection controller 3 converts the outputs (analog values) to an X coordinate value and Y coordinate value, and an output controller 4 outputs them.
Preferably, the magnet is disposed in such a manner that its magnetization axis coincides with the centerline of the Hall effect device array, that is, with the symmetry line, and a reference position is determined such that the magnetic flux density becomes symmetric with respect to the centerline of the Hall effect device array. In this case, since the Hall effect devices, which are placed at the position symmetric with respect to the centerline, generate the differential outputs, the differential output becomes zero at the reference position in an ideal case where the Hall effect devices have no variations or error in performance.
As the magnet moves, the differential amplifiers 2 produce their outputs in response to the movement. The detection controller 3 converts the outputs (analog values) to the X coordinate value and Y coordinate value, and the output controller 4 outputs them. It is not always necessary for the outputs at the reference position to be zero. An accurate displacement can be obtained by detecting the difference of the differential outputs of the Hall effect devices corresponding to the disposition of the magnet with reference to their differential outputs at the reference position.
As an example of a support structure enabling the movement of the magnet, a construction as shown in FIG. 5 has been proposed. It is configured such that a coiled spring 34 supports a magnet 32 at its end, and that magnetic sensors 31, which are disposed on a printed circuit board on which the coiled spring 34 is mounted, detect the movement of the magnet 32.
Another support structure of the magnet is configured as shown in FIG. 6. It includes a magnet case 45 containing a magnet 42, a coiled spring 44 attached to an end of the magnet case 45 via a coiled spring holder 46, and a magnet actuator 47 for supporting the coiled spring 44.
An ordinary touch type pointing device is configured such that two sets of comb-like electrodes are formed on a printed circuit board, and a conductive rubber is pressed thereon to vary the conducting state, and to output the coordinate values as digital values.
However, a problem common to these magnet support structures of the magnetic detecting type pointing devices is that they require not only the magnet, but also a variety of other components such as a coiled spring or magnet case. In particular, using the coiled spring presents a problem such as positioning the magnet at the origin in the assembly. In addition, they have a problem of hindering the size reduction of the pointing devices because the support structures are considerably greater than the magnet itself.
In summary, the conventional techniques have problems of requiring a complicated magnet support structure to support the magnet thereon, and of being difficult to assemble them and to downsize them. Furthermore, as for the touch type pointing device, since the conductive rubber is pressed every time the input is made, it is unavoidable that the repeated input can impair the conductive rubber, thereby reducing its life.
Japanese patent Application publication No. 7-117876 (1995) discloses a pointing control device for moving a pointer or cursor on a computer display to a desired position on the display. The pointing control device has its slider be moved along a dome, and has magnetic sensors detect magnetic flux changes from a magnet attached to the slider.
However, this type of the pointing device has a problem of being it difficult to form a thin-structure because the magnet is inclined along the dome, thereby leaving room for improvement in the thin-structure of the device and in the ease of operation. In addition, it has been desired to develop a manipulation adapter for making the operation of the pointing device easier.
The present invention is implemented to solve these problems. Therefore an object of the present invention is to provide a pointing device capable of facilitating the assembly, downsizing and prolonging the life.
Another object of the present invention is to provide a pointing device with a high degree of ease of use, which has a thin-structure and generates a large output in case of using a magnet with a small magnetic force.
Still another object of the present invention is to provide a pointing device with a high degree of ease of use, which has a thin-walled structure and hence enables a large output using a magnet with a small magnetic force by using a magnetic sensor array, and its magnetic sensors capable of automatically aligning an initial position of the magnet used as a position input of the pointing device.
Another object of the present invention is to provide a pointing device manipulation adapter with a high degree of ease of use, which generates a large output in case of using a magnet with a small magnetic force.